In article ,
The Natural Philosopher wrote:
On 15/04/2019 10:11, charles wrote:
In article l.net,
Dave Liquorice wrote:
On Sun, 14 Apr 2019 08:00:12 +0100, Brian Gaff wrote:

its affected by proximity, sounds more like a parasitic oscillation of
some sort.

That's what I'd be looking for. Monitor the cuurent draw, does it
follow the buzz level? The buzz is a symptom of the PSU running out
of steam, do the driver chips/transistors get warm/hot?

As it takes a while to appear and does so slowly I'd guess that it's
only just unstable and requires a signal to kick it off.

as I said - check the power supply.

bad decoupling cap feeding high impedance source that picks up hum from
the body once the cap has stopped being a cap.

Did you actually read my post? The buzz stops as you approach the device.
But perhaps your body is out of phase. ;-)

--
*Forget the Joneses, I keep us up with the Simpsons.

Dave Plowman London SW
To e-mail, change noise into sound.